Use of adenylate cyclase or bacteria producing it as vaccines against bordetella

ABSTRACT

The invention relates to a method for immunizing a mammal against infection by a first Bordetella species. The method comprises administering to the mammal a preparation comprising a portion of the amino acid sequence of mature adenylate cyclase of a second Bordetella species. The invention also relates to vaccine preparations comprising a portion of the amino acid sequence of mature adenylate cyclase from Bordetella species.

This application is a continuation, of application Ser. No. 07/623,706 filed Jan. 14, 1991, now abandoned.

The invention relates to vaccines capable of protecting man or animals against lethal infections caused by the Bordetella. It relates, in particular, to the use of vaccinating preparations developed from Bordetella or more particularly from adenylate cyclase produced by these bacteria as protective antigens against the toxic effects of the infections due to Bordetella.

It is known that the Bordetella, more particularly Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica, are responsible for respiratory diseases in the vertebrates.

Thus, in man, B.pertussis is responsible for whooping cough, an infantile disease very wide spread throughout the world.

The vaccination against whooping cough has hitherto been most usually carried out with the aid of inactivated whole bacteria.

However, such vaccines are not always devoid of toxicity in view of the fact that the virulence factors are constituted by proteins secreted by the bacteria and not by the bacteria themselves. The proteins can thus exert serious pathological effects, even after the death of the bacteria.

Among the determinants of virulence of B.pertussis, mention should be made of the adhesins such as the agglutinogens (AGG), the filamentous hemagglutinin (FHA) and the pertussis toxin (PTx), a cytotracheal toxin (CTT), a dermonecrotic toxin (DNT) and an adenylate cyclase-hemolysin (AC). The latter is synthesized in the form of a large precursor of 1706 residues. The amino-terminal part of the molecule bears the adenylate cyclase activity and the carboxy-terminal part possesses a strong homology with the Hly gene product of E.coli (hemolysin). This adenylate cyclase has the property of being activated by calmodulin.

The research for more suitable methods of prevention has led the inventors to study the role of each of the determinants of virulence and to develop an experimental model of infection mimicking the process of the natural disease.

These studies have made it possible to note the role of adenylate cyclase as cytotoxin and as protective antigen, and to develop a novel use of the vaccinating preparations based on adenylate cyclase or bacterial preparations producing adenylate cyclase.

The invention relates more particularly to the use of a bacterial vaccinating preparation developed from a given bacterium of the Bordetella genus, this use being characterized in that it is used to protect man or animals against the infections and the toxic effects caused by a bacterium of the Bordetella genus but different from that of the vaccinating preparation.

In accordance with another feature, the invention also relates to the use of a vaccinating preparation developed from an adenylate cyclase of a given bacterium of the Bordetella genus in order to protect man or animals against the infections and the toxic effects caused by a bacterium of the Bordetella genus different from that from which the adenylate cyclase is derived.

The bacteria of the Bordetella genus are selected from B.pertussis, B.parapertussis, and B.bronchiseptica.

In a preferred embodiment of the invention, the vaccinating preparation is developed from B.bronchiseptica or from the adenylate cyclase of B.bronchiseptica and is used to provide protection against the infections and the toxic effects caused by B.pertussis or B.parapertussis.

It should be noted that this crossed protection obtained starting from strains of B.bronchiseptica offers the advantage of using strains with more rapid growth than B.pertussis or B.parapertussis in order to develop vaccines against the infections caused by B.pertussis or B.parapertussis.

According to another embodiment of the invention, the vaccinating preparation is developed from B.pertussis or the adenylate cyclase of B.pertussis and is used to provide protection against the infections and the toxic effects caused by B.bronchiseptica or B.parapertussis.

According to yet another embodiment of the invention, the vaccinating preparation used is developed from B.parapertussis or the adenylate cyclase of B.parapertussis and is used to provide protection against the infections and the toxic effects caused by B.pertussis or B. bronchiseptica.

According to yet another embodiment of the invention, the vaccinating preparation used is developed from B.parapertussis or the adenylate cyclase of B.parapertussis and is used to provide protection against the infections and the toxic effects caused by B.pertussis or B.bronchiseptica.

The adenylate cyclase of the Bordetella to which reference has been made above is an adenylate cyclase such as that obtained by placing a supernatant of a bacterial culture of Bordetella in contact with an Affigel-calmodulin® gel.

More particularly, it is a preparation of adenylate cyclase such as those described in the application FR 2606789 filed on 17.11.86

It will be recalled that these preparations are characterized in that they possess a high purity and are almost completely devoid of contaminating bacterial products, in particular pertussis toxins, lipopolysaccharide (or LPS) and filamentous hemagglutinin (or FHA).

The adenylate cyclase of these preparations exists in a homogeneous form sedimenting on a sucrose density gradient with a coefficient S equal to 3.6. It exists in two structurally related, molecular forms of 45 and 43 kDa respectively.

Such preparations of adenylate cyclase possess an activity which may attain and even exceed 1600 μmole of cAMP min⁻¹ mg⁻¹.

Such preparations may be prepared from bacterial cultures expressing the AC (adenylate cyclase), more particularly from pathogenic bacteria whose AC is capable of interfering with the AC of eucaryotic cells, by placing a supernatant of bacterial cultures expressing the adenylate cyclase and concentrated beforehand or an extract of these bacteria in contact with calmodulin.

In order to obtain the enzyme in the free form, calmodulin fixed to a support is used, then the absorbed enzyme is recovered with the aid of a denaturing agent which is removed in turn, and the preparation of the free enzyme is recovered.

The support is more particularly constituted by a material inert with respect to the preparation containing the enzyme, and is capable of retaining molecules of high molecular weight, such as a gel or a filtering material.

The filtering material is advantageously made of nitro-cellulose or a plastic material and exhibits a porosity of 0.45 -0.22 μm.

The denaturing agent is preferably urea and preferably 4 to 8.8 M.

The concentrated supernatant of the bacterial culture is obtained by subjecting a supernatant of bacterial cultures expressing the AC to one or several filtration steps with the aid of nitrocellulose filters or filters of plastic material of porosity advantageously from 0.45 to 0.22 μm, then by incubating the filters with a detergent in order to release the AC and by removing from the AC preparation the insoluble materials present.

The detergent is, for example, Triton® or NP40®.

The bacterial extract is obtained by treatment of bacterial cells expressing the adenylate cyclase with urea and recovery of the supernatant.

As a variant, an adenylate cyclase is used such as that expressed by the nucleotide sequence given in the only figure with the corresponding amino acid sequence.

It will be obvious that the bases of the nucleotide sequence under consideration may be in an order different from that found in the genes and/or that these bases may be, where appropriate, substituted provided that a probe developed from such a sequence gives a characteristic and unequivocal response with regard to the capactity to recognize the presence of a gene coding for a protein with adenylate cyclase activity.

Any nucleotide sequence which can hybridize with this chain sequence such as that obtainable by reverse enzymatic transcription of the corresponding RNA or also by chemical synthesis is also included in the framework of the invention.

The above vaccinating preparations used may or may not be combined with the FHA and/or the PTx in the same inoculum.

In this latter case, the FHA is administered at the same time as the vaccinating preparation or at a different time. The preparations of FHA are advantageously obtained, for example, according to the method of SATO et al in Infect. Immun., 1983, 41, 310-320 or that of IMAIZUMI et al in Journal of Microbiol. Methods, 2, 334-347 (1984).

In accordance with another feature, the invention relates to vaccines capable of inducing a protection against the toxic effects and the infections caused by the Bordetella, molecular vaccines containing at least the active part of the amino acid sequence represented in the only figure, where appropiate, combined or not in the same inoculum with the FHA and/or the PTx.

These vaccines are advantageously used in conformity with the invention in order to carry out crossed protections.

In the implementation of the invention, the vaccinating preparations based on bacteria or the adenylate cyclase, advantageously purified, produced by these bacteria as well as the vaccines developed from recombinant adenylate cyclase are used at the usual doses and in the usual forms of administration, in particular in the standard forms which can be administered by the intranasal, oral or parenteral routes.

Other characteristics and advantages of the invention will become apparent in the description of the examples which follow and by referring to the only figure which shows the nucleotide sequence of the active part of the gene of B.pertussis coding for the adenylate cyclase and the corresponding sequence of amino acids.

The model of respiratory infection used in the assays reported in the examples is a model of infection by the intranasal route. The in vivo selection from a mouse lung infected by B.pertussis of a hyperpathogenic derivative of the virulent strain of B.pertussis 18323S (international reference strain for the evaluation tests of vaccines) has made it possible to observe in the adult mouse, after injection of bacteria by the intranasal route, an acute hemorrhagic edematous alveolitis (AHEA), lethal within 48-72 h.

The analyses of the products of the examples are performed as follows.

The activity of the AC is measured according to the method of White A. A. in Methods Enzymol., 38C, 41-46, 1974, as modified by Hanoune et al (J. Biol. Chem., 252, 2039-2046, 1977).

The activities of PTx and FHA are measured according to the method of TUOMANON S. and WEISS A. in J. Inf. Dis., 152, 118-125, 1985.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the nucleotide sequence of the active part of the gene of B. pertussis coding for the adenylate cyclase and the corresponding sequence of amino acids.

EXAMPLE 1

Culture of B.Bronchiseptica and Isolation of a Supernatant with a high concentration of Adenylate Cyclase.

A preculture of B.bronchiseptica 9.73, phase I and a spontaneously avirulent, stable variant of this strain, phase IV are grown for 48 hours at 36° C. on a modified Stainer-Scholte agar medium supplemented with cyclodextrin (according to IMAIZUIMI et al in J. Chim. Microbiol., 17, 781-786, 1983). The preculture is then transferred to a modified Stainer-Scholte liquid medium without cyclo-dextrin. The B.bronchiseptica 9.73 strain was isolated from the nostrils of a hare.

The liquid cultures are stirred at 150 rev./min. for 15 hours at 36° C. in a 1 liter Erlenmeyer containing 250 ml of medium. The culture is continued until an optical density OD₆₅₀ =1.2 ±0.2 is obtained. The bacteria are then removed by centrifugation at 5000 x g for 25 min.

The culture supernatants are stored at −30° C. until used or are concentrated immediately.

For the purposes of concentration, 3 liters of culture supernatant containing about 10 μg of proteins and 0.1 unit of enzyme per ml are filtered on filters of the Millipore® HAWP type of 0.45 μm. In this way, more than 90% of the enzymatic activity is retained on the filters. About 80% of this activity can be recuperated by incubation of the filters in 40 ml of a buffer A constituted by 50 mM Tris.HC1, pH 8 containing 6 mM of MgCl₂ and 0.1% of Triton X.100®. The insoluble material is removed by centrifugation for 30 min. at 15000 x g at 4° C. The specific activity of the concentrated culture supernatant is 115 units per milligram of protein.

A bacterial suspension of the strain 9.73 was injected into a mouse by the intranasal route; 48 hours later the lungs were excised and ground and a hemolytic clone was isolated, namely the clone 9.73S. This clone was deposited on 12 May 1989 with the CNCM under the No. I-858. This clone is hemolytic and synthesizes large amounts of adenylate cyclase. A bacterial suspension of this clone causes hemorrhagic edema in the lung of the mouse.

EXAMPLE 2 Procedure for the Isolation of Purified Extra-Cytoplasmic Adenylate Cyclase in the Free Form

40 ml of concentrated culture supernatant are added to 0.8 to 1 ml of Affigel-calmodulin® and the mixture is stirred slowly at 4° C. for 18 hours. More than {fraction (2/3 +L )}of the enzymatic activity is retained on the gel.

The Affigel-calmodulin is sedimented by centrifugation at 300 x g for 1 minute, it is washed several times with 0.5 M NaCl in buffer A. The adenylate cyclase is recovered from the gel with the aid of 2.5 ml of 8.8 M urea in buffer A. The urea is removed by filtration on a column of Sephadex G-25 ®, equilibrated with buffer A.

This enzymatic preparation possesses a specific activity of 1100 units/mg of protein.

It may be stored at −80° C. without loss of activity for several weeks.

EXAMPLE 3 Procedure for the Isolation of Purified Adenylate Cyclase from Bacterial Extracts.

A bacterial culture expressing AC activatable by calmodulin is subjected to a treatment with 8M urea for about 2 hours at room temperature. The supernatant which constitutes the bacterial extract is recovered and it is placed in contact with the Affigel-calmodulin gel under the conditions mentioned above.

An enzymatic preparation of high purity is obtained exhibiting approximately the same specific activity.

EXAMPLE 4 Study of the Secretion of AC, PTx and FHA, and the LD50 of Boretella Strains.

In table 1 below, are presented the results obtained by determining the factors of virulence AC, PTx and FHA and by measuring the LD50 (dose killing 50% of the mice in a batch) of different strains of Bordetella.

They are strains of B.pertussis (BP), B.parapertussis (BPP) and B.bronchiseptica (BB) corresponding either to hyperpathogenic strains, which secrete large amounts of adenylate cyclase (these strains bear the reference S in the table), or to parental strains of the hyperpathogenic strains.

TABLE 1 AC PTx FHA LD 50 BP18323 20 1 2 3 10⁸ BP18323S 180 4 2 10⁷ BP8144 2 (+) BP8144S 6 (+) BP8132 1 (+) 32 3.2 10⁸   BP8132S 3 (+) 32 <1.2 10⁸     BPP632 8 − 64 2 10⁸ BPP632S 35 − 64 <10⁸   BB973S 110 − 16 4 10⁸

These results reveal the high production of adenylate cyclase by hyperpathogenic strains, more particularly by B.bronchiseptica 973S and B.pertussis 18323S.

The secretion of PTx is also increased in the hyperpathogenic derivatives as the results relating to B.pertussis show whereas the secretion of FHA remains the same in the two strains.

B.bronchiseptica and B.parapertussis, which synthesize the same factors as B.pertussis with the exception of the PTx, induce a hemorrhagic edematous alveolitis in the mouse similar to that induced by B.pertussis. On the other hand, a strain derived from the virulent strain B.pertussis 8132, the strain B.P.348 accommodating a transposon Tn5 in the structural gene of the AC, inactivating the latter, is incapable of inducing a AHEA in the mouse. Nonetheless, this mutant secretes all of the other factors of virulence, in particular the PTx.

The body of these results designates the AC as the factor responsible for the hemorrhagic edematous alveolitis in the mouse.

EXAMPLE 5 1. Experiments of Active Protection Starting From Bacterial Vaccines

Protection experiments (against B.pertussis) were carried out with the aid of different bacterial vaccines (usually 3 sub-cutaneous injections of 250 μl of a bacterial suspension containing 10⁹ bacteria/ml, heated to 56° C. at weekly intervals).

In table 2 below are reported the results obtained by using strains of B.bronchiseptica 9.73S as well as strains of B.pertussis 18323S, B.parapertussis 63.25 and B.avium (Blike Hewouet) for the development of the bacterial vaccines.

The B.pertussis strain is administered two weeks after the last immunization: 50 μl of 10⁸ live bacteria of the B.pertussis 18323S strain are injected by the intranasal route.

LETHAL TEST STRAIN INJECTED (B. pertussis) 0 10/10  B. bronchiseptica 0/10 B. pertussis 0/10 B. parapertussis 3/10 B. avium 9/10

It will be noted that the mice vaccinated with the aid of preparations of B.bronchiseptica are completely protected against the lethal test with B.pertussis (crossed protection), like those vaccinated with B.pertussis.

On the other hand, the mice vaccinated with preparations of B.avium are not protected, which works in favour of the role of the AC in the induction of hemorrhagic edematous alveolitis.

2. Experiments of Active Protection Starting from Purified Antigens

Purified antigens are used.

The preparations of AC are purified either from the culture supernatant (70% of the enzyme is excreted by the bacterium), or from the bacteria by working advantageously according to the procedure of the patent application FR 2606789 of 17.11.86.

Mice were immunized with different doses of antigen (3 sub-cutaneous injections of 250 μl of antigen in 10 mM Tris buffer, pH 7, containing 1 mg/ml of Am⁺⁺⁺ at weekly intervals) before the lethal test with B.pertussis was made.

For the lethal test, 50 μl of a bacterial suspension of the virulent and hyperpathogenic strain 18323S is injected by the intranasal route 2 weeks after the last immunization. The bacterial concentration of the suspension is 10⁸ in test a, 2×10⁸ in test b, and 10⁷ in test c.

In table 3 below, the results are reported of the protection obtained against a strain of B.pertussis (BP 18323S) at different concentrations after injection of AC, recombinant AC of a vaccine, PTx and FHA.

The recombinant AC is advantageously such as described in the patent application FR 2621597 of 24.7.87. It is a fragment corresponding to the structural gene of the AC which could be expressed in E.coli. This fragment, which bears the adenylate cyclase activity and the binding site for calmodulin, was purified to homogeneity (see the figure).

AC AC_(rec) VACCIN PTx FHA 0 a: lethal test B.P. 18323S 10/LD50 3/0.9 μg 3/1.5 μg 3/10⁹b 2/2 μg 2/10 μg 9/12 1/10 0/40 9/22 20/22 20/22 b: lethal test B.P. 18323S 20/LD50   3/2 μg 3/10⁹b 5/10 3/10 10/10 c: lethal test B.P. 18323S 1/LD50   3/6 μg   3/6 μg 3/18 μg 3/2 μg 3/10 μg 0/10 0/10 0/10 0/10  5/10  5/10

The results of lethality are expressed as the number of dead mice over the total number of mice.

The results obtained show the production of a synthesis of anti-AC antibodies and a protection of the mice after immunization with AC (three immunizations of 1.5 μl of AC). This protection is almost complete when the lethal test is performed with a number of bacteria equal to (10⁷ live bacteria) or 10 times higher than the lethal dose 50 (10⁸ live bacteria); it is 60% when the lethal test is performed with a number of bacteria equal to 20 times the lethal dose 50 (2.10⁸ lethal bacteria).

Complete protection was obtained after immunization of mice with the recombinant AC when the lethal test was performed with a number of bacteria equal to the lethal dose 50. The immunizations performed with FHA did not show a protective effect of this toxin in spite of the presence of antibodies in the mice immunized even when the lethal test was performed with a small number of bacteria.

The experiments conducted with the PTx show a partial protection after two immunizations with 2 μg of PTx when the lethal test is 10 times higher than the lethal dose 50 but it must be pointed out that, in this case, the synthesis of anti-PTx antibodies is very low. When the mice are immunized with 3 times 2 μg of PTx, the synthesis of antibodies is much greater and we obtain complete protection when the lethal test is performed with a number of bacteria equal to the lethal dose 50.

In sum, these results show that the adenylate cyclase constitutes the cytotoxin responsible for the hemorrhagic edematous alveolitis observed in the mouse infected by B.pertussis and constitutes an antigen protecting against such lesions. The PTx and the FHA would appear to play no role in the induction of this AHEA but could be protective antigens of such lesions by inhibiting the adhesion of bacteria to the respiratory epithelium. 

What is claimed is:
 1. A method for protecting against toxic effects of infection by a first Bordetella species in a mammal, comprising administering to said mammal a preparation comprising purified adenylate cyclase of a second Bordetella species in an amount sufficient to protect against the toxic effects of said first Bordetella species, wherein: (a) said purified adenylate cyclase has a molecular weight of 43 or 45 kDa and a calmodulin binding site; (b) said first Bordetella species is Bordetella pertussis; and (c) said second Bordetella species is Bordetella bronchiseptica.
 2. A method for protecting against toxic effects of infection by a first Bordetella species in a mammal, comprising administering to said mammal a preparation comprising purified adenylate cyclase of a second Bordetella species in an amount sufficient to protect against the toxic effects of said first Bordetella species, wherein: (a) said purified adenylate cyclase has a molecular weight of 43 or 45 kDa and a calmodulin binding site; (b) said first Bordetella species is Bordetella parapertussis; and (c) said second Bordetella species is Bordetella bronchiseptica.
 3. A method for protecting against toxic effects of infection by a first Bordetella species in a mammal, comprising administering to said mammal a preparation comprising purified adenylate cyclase of a second Bordetella species in an amount sufficient to protect against the toxic effects of said first Bordetella species, wherein: (a) said purified adenylate cyclase has a molecular weight of 43 or 45 kDa and a calmodulin binding site; (b) said first Bordetella species is Bordetella bronchiseptica; and (c) said second Bordetella species is Bordetella pertussis.
 4. The method of any one of claims 1 to 3, wherein said adenylate cyclase exhibits adenylate cyclase activity and comprises the binding site for calmodulin.
 5. The method of any one of claims 1 to 3, wherein said method further comprises administering to said mammal at least one protein selected from the group consisting of filamentous hemaggulutnin and pertussis toxin.
 6. A method for protecting against toxic effects of infection by a first Bordetella species in a mammal, comprising administering to said mammal a preparation comprising purified adenylate cyclase of a second Bordetella species in an amount sufficient to protect against the toxic effects of said first Bordetella species, wherein: (a) said purified adenylate cyclase has a molecular weight of 43 or 45 kDa and a calmodulin binding site; and (b) said second Bordetella species is Bordetella bronchiseptica; and (c) said first Bordetella species is different from said second Bordetella species.
 7. A method for protecting against toxic effects of infection by a first Bordetella species in a mammal, comprising administering to said mammal a preparation comprising purified adenylate cyclase of a second Bordetella species in an amount sufficient to protect against the toxic effects of said first Bordetella species, wherein: (a) said purified adenylate cyclase has a molecular weight of 43 or 45 kDa and a calmodulin binding site; and (b) said second Bordetella species is Bordetella bronchiseptica; and (c) said first Bordetella species is Bordetella pertussis or Bordetella parapertussis. 